“If in the rare circumstances it falls to the hands of Isis, it will be their downfall. They will need constant logistical local supply to stay in Tora Bora.”

Government forces have launched new operations targeting ISIS, but more fighters are being recruited or crossing the border from Pakistan, said Attahullah Khogyani, spokesman for the Nangarhar governor’s office.

“You kill one Daesh fighter and 10 more come from the border or are recruited here,” he said.

General John Nicholson, the chief US commander in Afghanistan, has vowed to defeat ISIS in Afghanistan this year.

In April used one of the largest conventional bombs ever dropped in combat to target a cave complex used by the terror group in the nearby district of Achin.